The construction and installation of various structures such as buildings, bridges and towers requires the use of load lifting equipment suitable for the project location and intended purpose. Economic considerations dictate that the equipment used involve minimum capital investment, be transportable and, if necessary, assembled and erected in a reasonable amount of time. These limitations present rather acute problems when high structures such as elevated water tanks, highway overpasses and bridge support columns are erected. Erecting load lifting equipment for constructing high structures desirably requires a minimum of ancillary mechanical equipment so as to reduce labor and related costs. To do this, however, necessitates that the final load lifting equipment have self-contained features which permit it to at least partially lift and erect itself and, after the job is done, be demountable and disassembled largely by means of its own elements and components.
Hines U.S. Pat. Nos. 2,720,694; 2,754,012 and 2,768,432 disclose apparatus and methods of erecting elevated structures, and especially elevated water tanks. The apparatus and methods disclosed in these patents have been used industrially, in slightly modified variations, for about thirty to forty years. There are at least several important disadvantages to use of the prior art system. These include a need to have a second or auxiliary crane on the project, a bolting ring on the derrick, undesirably high freight costs and rigging labor costs and a complicated erection sequence and a lack of flexibility for use on a wide variety of jobs. There is thus a need for alternative apparatus for erecting high structures.